1. Technical Field
The present invention relates to a robot.
2. Related Art
In the related art, a robot having a base and a plurality of arm link portions is known (for example, refer to JP-A-10-100085). Each arm link portion is rotatably coupled to the arm link portion on a base end side via a joint portion, and the arm link portion closest to the base side is rotatably coupled to the base via a joint portion.
In such a robot, the rigidity of the joint portion that couples the base and the arm link portion or the rigidity of the joint portion that couples the arm link portion and the arm link portion is low compared to the base or the arm link portions under the influence of spring elements of the joint portions. For the reason, there is a problem in that vibration may be easily generated in the arm link portions due to the rotation of the arm link portions or disturbance applied to the arm link portions.
Thus, in the robot described in JP-A-10-100085, an acceleration sensor is installed at a tip portion of the arm link portion closest to a tip side of the robot, compensation components of the respective joint portions that compensate command values to motors of the respective joint portions so as to suppress the vibration generated at the tip portion of the arm link portion closest to the tip side are calculated on the basis of the acceleration detected by the acceleration sensor, and the calculated compensation components of the respective joint portions are subtracted from the command values of the corresponding respective joint portions.
However, the robot described in JP-A-10-100085 has the following drawbacks.
First, since the acceleration sensor is installed at the tip portion of the arm link portion closest to the tip side, the acceleration detected by the acceleration sensor is converted and corrected into those for the respective joint portions. At this time, since it is necessary to perform coordinate axis transformation referred to as the Jacobi's transformation, and matrix calculation having a number of products of sine and cosine as factors is required, the amount of calculation becomes huge. Since it is necessary to calculate the factors according to the rotation angles of the motors of the respective joint portions that change every moment, it is always necessary to execute huge calculation. Accordingly, there is a drawback in that response speed becomes slow.
Additionally, since accurate acceleration or speed cannot be fed back if calculation precision declines, vibration suppression capability may decline or control performance may be impaired. For this reason, there is a restriction on the design of a control system in that a high-speed computing unit is required, for example.
Additionally, in the calculation of the coordinate axis transformation, there is a region (incalculable region) with no coordinate axis transformation solution referred to as a singular point. In the region, the vibration suppression capability may decline or vibration may be increased instead.
Additionally, for example, even when the posture of an arm link portion varies, such as when the arm link portion is extended and when the arm link portion is folded, the same control is performed. Thus, it is difficult to precisely suppress vibration while stabilizing control.